The present invention relates to an infrared data communication module used for performing infrared data communication by IrDA (Infrared Data Association) method.
Infrared data communication modules (hereinafter simply referred to as xe2x80x9cmodulexe2x80x9d) based on the IrDA are increasingly used for notebook-size personal computers, and recently also for mobile phones and electronic organizers. A module of this kind incorporates, in one package, not only an infrared light emitting element and an infrared light receiving element but also an IC chip for controlling these elements for enabling wireless communications between the above-described electronic apparatuses or between such an apparatus and a peripheral device such as a printer. In such a module, the communication speed and the communication distance are standardized in accordance with the versions, and attempts are being made to enhance the infrared data communication performance. On the other hand, there is an increasing demand for a size-reduction of the module, as a whole. Further, the manufacturing process requires a high dimensional accuracy and a cost reduction.
A prior art infrared data communication module of this kind is shown in FIG. 17. FIG. 18 illustrates the internal structure of the infrared data communication module of FIG. 17, whereas FIG. 19 is a sectional view taken along lines XIXxe2x80x94XIX of FIG. 17. As shown in FIG. 17, the prior art module 100 comprises a substrate 101 having a surface 101a for mounting a group E of components, and a molded body 5 formed from a molding resin integrally on the substrate 101. The group E of components includes a light emitting element 2, a light receiving element 3 and an IC chip 4. As shown in FIG. 19, the light emitting element 2, the light receiving element 3 and the IC chip 4 are respectively covered with protective members 6 within the molded body 5.
The light emitting element 2, which is an infrared emitting diode capable of emitting infrared light, has a rectangular configuration provided by cutting a semiconductor wafer including a light emitting layer. The light emitting element 2 is provided, at the bottom surface thereof, with a full electrode formed of gold, and is mounted on the substrate 101 with the full electrode oriented downward. The light emitting element 2 is formed, on the upper surface opposite to the full electrode, with a partial electrode formed of gold. Of the light emitted from the light emitting layer, the light emitted upward through the upper surface of the light emitting element 2 is mainly utilized to provide signals for data communication. In this prior art module, the light receiving element 3 is formed of a PIN photo diode capable of detecting infrared light and has an upper surface formed with a plurality of electrodes. The IC chip 4 controls the infrared emission and reception of the light emitting element 2 and the light receiving element 3, respectively and has an upper surface formed with a plurality of electrodes.
As shown in FIG. 18, the substrate 101 is formed of an insulating material such as a glass fiber-reinforced epoxy resin and generally rectangular as viewed in plan. One of the longitudinal edges of the substrate 1 is formed with a plurality of inwardly convex semi-cylindrical terminals 19. The surface 101a of the substrate 101 is provided with a predetermined wiring pattern P or the like which is electrically connected to the terminals 19 and formed by etching a conductive film.
After the mounting onto the surface 101a of the substrate 101 at predetermined positions, the group E of components, particularly the light receiving element 3 and the IC chip 4, are electrically connected, via gold wires W, to wire-bonding pads 7 forming part of the wiring pattern P by first bonding and second bonding. Specifically, in the first bonding, a gold wire is introduced into a jig called capillary so that the tip end of the wire projects outward from the tip end of the capillary, and the tip end of the wire is melted by heating with hydrogen flame to form a gold ball. Then, by moving the capillary, the gold ball is pressed onto the electrode of the light receiving element 3 (or the IC chip 4) for fixation thereto, thereby completing the first bonding. In the second bonding, the gold wire is extended out of the capillary and guided toward the wire bonding pad 7 with the tip end of the gold wire, i.e. the gold ball fixed. The gold wire is then pressed against the upper surface of the wire bonding pad 7 utilizing the tip end of the capillary while applying ultrasonic vibrations thereto, thereby second-bonding the wire. When the gold wire is fixed under pressure onto the wire bonding pad 7, the gold wire is pressed and cut while slidably moving the capillary. Thus, the wire bonding step is completed. The wire bonding pads 7 are formed by plating part of the wiring pattern P (conductive film) with gold to provide good conduction with the gold wires W. In this way, each of the light receiving element 2 and the IC chip 4 is connected to the corresponding terminals 19.
The connection between the light emitting element 2 and the IC chip 4 (and between the light receiving element 3 and the IC chip 4) is carried out by wire bonding. However, when these elements are directly connected to each other, either the light emitting element (light receiving element 3) or the IC chip 4 is pressed by the capillary in the wire bonding and may be therefore broken. Moreover, since each of the electrodes of the light emitting element 2 (light receiving element 3) and the IC chip 4 is extremely small, it may not be possible to fix a gold wire to the electrode with a large contact area in the second bonding, which may lead to the deterioration of the data communication performance of the infrared data communication module 100. Therefore, as shown in FIG. 18, for preventing the breakage of the elements and the deterioration of the data communication performance, the connection between the light emitting element 2 and the IC chip 4 and between the light receiving element 3 and the IC chip 4 is carried out via jumper pads 11a, 11b of a relatively large surface area formed on the surface 101a of the substrate 101 instead of directly connecting these elements. Specifically, the light emitting element 2 is connected to the jumper pad 11a by wire bonding, whereas the IC chip 4 is connected to the jumper pads 11a and 11b by wire bonding.
Similarly to the die bonding pad, the jumper pads 11a, 11b are formed by plating a conductive film with gold to provide a good conductivity with the gold wires. Specifically, the jumper pad 11a (jumper pad 11b) is obtained by forming a plating conductive pattern 112a (plating conducive pattern 112b) from a conductive film on the surface 101a of the substrate 101 followed by applying a gold foil to the conductive pattern 112a at the region to become the jumper pad 11a (jumper pad 11b) by flowing a current through the plating conductive pattern 112a (plating conductive pattern 112b). The plating conductive patterns 112a, 112b are formed at the same time as forming the wiring pattern P.
As shown in FIG. 18, the connection between the light emitting element 2 and the terminal 19 is performed by bonding the light emitting element 2 onto the die bonding pad 113 electrically connected to the terminal 19. The die bonding pad 113 is formed by plating a conductive film with gold to provide a good conductivity with the full electrode formed on the bottom surface of the light emitting element 2. Specifically, the die bonding pad 113 is obtained by forming an LED conductive pattern 114 from a conductive film on the surface 101a of the substrate 101 followed by applying a gold foil to part of the LED conductive pattern 114 by electroplating by flowing a current through the LED conductive pattern 114. Similarly to the plating conductive pattern 112, the LED conductive pattern 114 is formed at the same time as forming the wiring pattern P. The die bonding pad 113 is so formed to have a minimum size required for bonding the light emitting element 2. Specifically, the die bonding pad 113 is rectangular in plan view and has an area slightly larger than the bottom surface area of the light emitting element 2.
As shown in FIGS. 17 and 19, the molded body 5 seals the above-described group E of components from above the protective members 6 while covering the entirety of the surface 1a of the substrate 1. The molded body 5 is formed of a molding resin which blocks visible light while passing infrared light. The molded body 5 is integrally formed with the light emitting lens 51 in facing relationship to the light emitting element 2 for converging the light emitted through the upper surface of the light emitting element 2 for emission. Further, the molded body 5 is integrally formed with a light receiving lens 52 in facing relationship to the light receiving element 3.
The protective members 6 function to alleviate the stress caused by the molding resin in forming the molded body 5 to prevent these elements from breaking due to such stress. Before the formation of the molded body 5, the protective members 6 are formed by applying a thermosetting resin such as a silicone resin in a gel state to each of the elements 2, 3, 4 and then hardening the resin.
As shown in FIG. 17, the outer surfaces of the module A provided in the above-described manner may be partially covered with a shield case 9 formed of a metal (while exposing the light emitting lens 51, the light receiving lens 52 and the terminals 19) for preventing external electromagnetic noises and infrared light from adversely affecting the IC chip 4. The shield case 9 is provided, at a surface for contacting the molded body 5, with a riser portion 91 which inwardly slants toward the molded body 5 and a fitting portion 93 for fitting into a recess 92 formed on a surface of the molded body 5. Since the riser portion 91 and the fitting portion 93 prevent the detachment of the shield case 9 from the module 100, the shield case 100 can be fixed to the module 100 without the use of an adhesive.
For enhancing the manufacturing efficiency, the module 100 is formed from a material board 110 which includes a plurality of areas for substrates 101 arranged in rows and columns, as shown in FIG. 20. Specifically, a multiplicity of modules 100 are obtained by mounting groups E of elements on the material board 110, forming protective members 6 and molded bodies 5 successively from above, and dividing the board into each of the substrates 101. Specifically, the molded bodies 5 are formed by molding a resin into intermediate sealing bodies 5a each of which is larger, in plan view, than the predetermined size of a molded body 5 and then removing unnecessary portions of each intermediate sealing body 5a in dividing the material board into each of the substrates 101. Thus, the molded body 5 is integrally formed on the substrate 101.
However, the prior art module 100 has the following drawbacks due to the above-described structure.
In the case where modules 100 are formed from a material board 110, the plating conductive patterns 112a, 112b of one substrate 101 need be electrically connected to those of other substrates 101 so that electroplating can be carried out collectively with respect to the plural substrates 101 of the material board 110. For this purpose, as shown in FIG. 18, the plating conductive patterns 112a, 112b of each substrate 101 include respective connecting portions 112axe2x80x2, 112bxe2x80x2 extending outward from the edges of the substrate 101. The connecting portions 112axe2x80x2, 112bxe2x80x2 are cut in dividing the material board 110 into each of the substrates. As a result, in the case of the connecting portion 112bxe2x80x2, for example, its end surfaces 112bxe2x80x3 are exposed at the side surface of the module 100, as shown in FIG. 19. Similarly, the end surfaces of the connecting portion 112axe2x80x2 are exposed at the side surface of the module 100. Therefore, when a shield case 9 is attached to the module 100, the end surfaces of the connecting portions 112axe2x80x2, 112bxe2x80x2 may contact the shield case 9. As a result, the jumper pads 11a and 11b may be electrically connected to each other via the shield case 9, causing a problem of short-circuiting of the module 100.
Moreover, in the prior art module 100, although light is emitted radially from the light emitting layer in the light emitting element 2, the light emitted through the upper surface of the light emitting element 2 is mainly utilized while wasting the light emitted through the side surfaces of the light emitting element 2. Therefore, the light emitted from the light emitting element 2 is not utilized efficiently.
Further, when an excessive amount of thermosetting resin in a gel state is applied in forming the protective members 6, the thermosetting resin may spread around each of the elements 2, 3 and 4 on the surface 101a of the substrate 101. As a result, in forming the molded body 5, a sufficient contact area may not be provided between the substrate 101 and the molded body 5, which deteriorates the bonding strength between the substrate 101 and the molded body 5. Thus, the two members may be released from each other at the interface, which may result in breakage of the gold wires W or removal of the group E of components.
The present invention is conceived under the circumstances described above. It is, therefore, an object of the present invention to provide an infrared data communication module which is capable of preventing short-circuiting.
Another object of the present invention is to provide an infrared data communication module capable of efficiently utilizing the light emitted from the light emitting element.
Still another object of the present invention is to provide an infrared data communication module capable of enhancing the bond between the substrate and the molded body.
According to a first aspect of the present invention, there is provided an infrared data communication module comprising a substrate having a surface for mounting a group of components which includes a light emitting element, a light receiving element and an IC element, and a molded body formed of a molding resin to entirely cover said surface of the substrate for sealing the group of components. The surface of the substrate is formed with one or a plurality of jumper pads formed by plating a conductive film with gold. Each jumper pad is partially or entirely spaced from an edge of the substrate.
Preferably, outer surfaces of the module are partially covered with a shield case formed of a metal.
Preferably, the shield case is provided, at a surface for contacting the molded body, with either one or both of a riser portion which inwardly slants toward the molded body and a fitting portion for fitting into a recess formed on a surface of the molded body.
According to a second aspect of the present invention, there is provided an infrared data communication module comprising a substrate having a surface provided with a die bonding pad formed by plating a conductive film with gold, and a light emitting element mounted on the die bonding pad. The die bonding pad is generally circular as viewed in plan and has an area larger than a bottom surface area of the light emitting element.
According to a third aspect of the present invention, there is provided an infrared data communication module comprising a substrate having a surface for mounting a light emitting element, a light receiving element and an IC element, a protective member for covering each of the elements, and a molded body formed of a molding resin on said surface of the substrate to cover the protective member. The surface of the substrate is formed with a recess for enhancing bond between the substrate and the molded body.
Preferably, the recess is formed on said surface of the substrate at each of plural portions which avoid the protective member.
Preferably, the recess is generally cylindrical.
According to a fourth aspect of the present invention, there is provided a method of making infrared data communication modules each of which comprises a substrate having a surface for mounting a group of components which includes a light emitting element, a light receiving element and an IC element, and a molded body formed of a molding resin to entirely cover said surface of the substrate for sealing the group of components. The surface of the substrate is formed with one or a plurality of jumper pads formed by plating a conductive film with gold. The method comprises the steps of forming a conductive film on an entire surface of a material board including substrate areas which later provide substrates, etching the conductive film to form a plating conductive pattern which later provides jumper pads, applying a gold foil on the plating conductive pattern by electroplating at jumper pad regions which correspond to the jumper pads, removing a connecting portion of the plating conductive pattern extending from an edge of each substrate area to outside of the substrate area, mounting groups of elements, shaping a molding rein into molded bodies on the material board, and dividing the material board along each of the substrate areas.
According to a fifth aspect of the present invention, there is provided a method of making an infrared data communication module which comprises a substrate having a surface for mounting a group of components including a light emitting element, a light receiving element and an IC element, and a molded body formed of a molding resin to seal the group of components. The method comprises the steps of forming a recess on said surface of the substrate for enhancing bond between the substrate and the molded body before the group of components is mounted on the substrate, forming the molded body so that the molding resin is trapped and hardened in the recess after the group of components is mounted on the substrate.
Other features and advantages of the present invention will become clearer from the detailed description given below with reference to the accompanying drawings.